Heat treatment of alloys



v calcium borate.

Patented Mar. 27, i928 res earsar QFFIQEQ KARL J'. JAGOI BI, OF BOSELLE, NEW JERSEY, ASSIGNOR TO PAGIFIC COAST BORAX COMPANY, OF NEW YORK, N. Y., A CORPORATIGN OF NEVADA.

HEAT TBEATMENTEOF ALLOYS. v

, No Drawing. Application filed June 9,

This invention relates to improvements in the tempering or heat treatment of alloy steels and particularly of high speed tool steels or of high speed tools made 'of alloy 5 steels.

According to the present invention, the tempering or heat treatment of the tools, etc. is effected in a fused bath of a borate which is substantially neutral in reaction, such as Such a bath, e. g. of calcium borate is neutral in the sense that it does not attack-the alloy steel in an objectionable way, as does a bath of borax.

In the practice of the invention, two baths may advantageously be used, the first a preheating bath and the second the ,main telnpering or heat treatment bath. For example, a preheating bath of calcium bi-borate- CaB O may be used for bringing the temperature of the high speed tools up to around 1800 F. and the main bath may be maintained at a temperature, e. g. around 2250 F. and the tools, after having been heated in the preheating bath to approximately the temperature of that hath can then be transferred to-the main bath and kept therein for a sufficient period of time to complete the heat treating operation. With the baths at a constant temperature, it can readily be determined-ho long it takes to bring the tools to the temper ture of the bath and they can thereafter be kept in the bath for a limited time, e. g. a period of around 9 to 10 minutes in the preheating bath, and about 3 minutes in the hardening bath after which they may be removed and put in a cooling bath at a lower temperature, e. g. at a temperature around 1000? F.

The cooling bath into which the tools are 4 placed, may advantageously be a bath containing sodium carbonate. The calcium boabout 1000 F.

1926... Serial No. 114,807.

rate ren'lains on the tools when removed,

from the bath, in the form of a thin film, but by dipping the tempered or heat treated tools in a bath containing sodium carbonate, e. g. at 1000 F., this film of calcium borate will ,be'removed at the same time that the tool is cooled to the temperature of this bath. The tools can then be further cooled or quenched by plunging them in an oil bath.

Instead ofusing calcium borate, other stable neutral borates, such as other alkali earth borates, can be similarly used.

The temperature of the tempering or heat treatment can be varied with different alloy steels, or with different tools, and the invention is not limited to the specific example 4. The method of removing a calcium biborate film remaining on an article after treatment according to claim 2, which consists in immersing the article containing the film ina bath containing sodium carbonate, said bath being at a temperature of about 1000 F.

In testimonywhereof I affix my signature.

KARL J. JACOBI. 

